(CNN) — The US Supreme Court on Friday left in place a Pennsylvania court ruling that is expected to expand options for voters whose mail-in ballots are rejected for technical reasons to have their votes counted, in a defeat for Republicans in a critical battleground state.

There were no noted dissents.

For Pennsylvania voters who made a mistake in how they prepared their mail-in ballots, it could ensure they have a backup option to have a provisional ballot counted.

It’s unclear how many Pennsylvania voters will benefit because not every county notifies voters of defective mail ballots. But both sides in the appeal before the Supreme Court characterized the dispute as affecting potentially “thousands” of votes at a minimum.

Conservative Justice Samuel Alito wrote a brief statement – which was joined by Justices Clarence Thomas and Neil Gorsuch – essentially arguing that the court couldn’t give the Republicans who brought the appeal what they had sought even if it wanted to.

The case, Alito wrote, “is a matter of considerable importance.” But, he wrote, “even if we agreed with the applicants’ federal constitutional argument (a question on which I express no view at this time), we could not prevent the consequences they fear.”

Republicans had asked the Supreme Court in an emergency appeal this week to block a state court ruling that allowed provisional ballots to be counted in cases where voters failed to enclose them in “secrecy” sleeves before mailing them in.

Though the case was technically limited to two voters in a single county, the Republican National Committee had framed the dispute as having much wider implications, asking the court to either pause the lower court’s ruling or, alternatively, to segregate the ballots at issue statewide.

Ari Savitzky, senior staff attorney at the ACLU’s Voting Rights Project, which had represented the voters, called the ruling a “win for democracy and the rule of law.” “The court rightly rejected this eleventh-hour attempt to discount the votes of Pennsylvanians and interfere in the state’s electoral process. The bottom line is that voters deserve to have their voices heard,” he said.

The RNC did not immediately respond to a request for comment.

The high court’s decision came on the heels of another order on Wednesday in which a conservative majority allowed Virginia to purge an estimated 1,600 voters from its registration rolls. Republicans said those registrants were self-identified noncitizens. Voting rights groups said at least some eligible US citizens were ensnared. The Virginia order drew sharp criticism from voting and immigrant rights groups in part because the court offered no explanation for its decision.

‘Naked’ and other defective mail-in ballots

The initial lawsuit was focused on sleeveless, so-called “naked ballots.” But both the ACLU and the RNC suggested in their briefs that the case could affect other types of defective mail-in ballots, such as those missing required signatures and dates on the envelope.

Different counties in Pennsylvania have different procedures for dealing with defective mail ballots, some more forgiving than others. That patchwork of rules makes it difficult to say with certainty how many ballots were at stake in the case. In its appeal, the RNC said the case could potentially affect “tens of thousands of votes in a state which many anticipate could be decisive.” In its response, the ACLU said “potentially thousands” of ballots were in play.

Four years ago, President Joe Biden beat former President Donald Trump in Pennsylvania by more than 80,000 votes. Polls indicate that, this year, Trump and Vice President Kamala Harris are in a dead heat.

The suit was filed by two voters in Butler County who submitted mail-in ballots but failed to enclose those ballots in the secrecy sleeve before placing them in an outer mailing envelope. A machine scanner identified the problem and the voters received an automated message alerting them that their vote would not be counted.

The voters showed up at their precincts during the state’s primary election and attempted to cast provisional ballots but learned those votes would also not be counted. County election officials said state law barred them from voting because they had already submitted a mail-in ballot, even though that ballot was defective.

Pennsylvania’s top court sided with the voters, ruling that election officials were correct to toss the mail-in ballots but “erred in refusing to count” the provisional ballots. Pennsylvania law, the state’s high court ruled, requires provisional ballots “be counted if there were no other ballots attributable to the electors. There were none.”

Republicans told the US Supreme Court that Pennsylvania’s courts usurped power reserved to the state legislature by allowing voters to cast provisional ballots after their mail-in ballots were tossed out. That’s because state law bars election officials from counting a provisional ballot if a mail-in ballot is “timely received by a county board of elections.”

“That,” Republicans told the Supreme Court, “should be the end of the case.”

But Democrats who intervened in the case, voting rights groups and state and county election officials said that reading of the law would lead to the “absurd” result that some residents could be blocked from casting a vote because of a technical error – despite the fact that the state had in a place a provisional ballot system that was intended to serve as a backup.

Just under the surface of the Pennsylvania dispute were several broader legal fights dealing with when the Supreme Court can intervene in a state election fight – questions that could have nationwide implications.

The RNC had argued that Pennsylvania’s Supreme Court violated the so-called Purcell principle, which generally warns courts against getting involved in last-minute election disputes over state law. But the voting rights groups noted the Supreme Court had previously framed Purcell as a check on federal – not state – courts.

Also at issue was whether the Supreme Court had the power to review the case at all, given that it involved a state court reviewing state law. The RNC relied on an untested legal theory that the US Constitution gives state legislatures vast power to set election rules without oversight from state courts. The Supreme Court declined to take up that theory in a 2023 decision involving North Carolina’s redistricting, but it also didn’t close the door on reviewing state court decisions about state law if they “transgress the ordinary bounds of judicial review.”

Chief Justice John Roberts didn’t explain in his opinion in that case what those words mean. The RNC appeal appeared to be at least in part an effort to test the limits of the definition of “ordinary bounds.”

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